macOS has built-in tools for PDF-to-image. None of them are great for a multi-page document. Here's the full picture.
Preview's built-in export
Open the PDF in Preview. File > Export > pick JPG. Limitation: it only exports the currently visible page. For a multi-page PDF, you'd need to do it page by page.
For one page, Preview is the fastest. For a 20-page document, you'll lose your afternoon.
Automator for batches
macOS Automator has a "Render PDF Pages as JPEG" action. Build a Quick Action that takes a PDF and outputs JPGs. Works offline, free, no install. Setup takes 10 minutes the first time.
Worth doing if you convert PDFs to JPGs weekly. Not worth it for occasional use.
The browser route
Open Flint's PDF to JPG in Safari, drag the PDF onto the page, download the zip of JPGs. Works for any number of pages. No setup, no per-page clicking.
For most Mac users, this is the practical answer.
Quality settings on Mac
All three methods let you control DPI in some form. Preview's is buried; Automator's is explicit; Flint's is a dropdown. 300dpi is the safe default for any use that might be printed. 150dpi is fine for screen and messaging.
FAQ
Can Preview do all pages at once?
Not natively. Use Automator's batch action, or convert via browser.
Does it work offline?
Preview and Automator do; the browser route needs internet.
What about Quick Look?
Quick Look shows the PDF but can't export. Use one of the conversion paths.
Will Apple Silicon affect anything?
No — all three methods work identically on M-series Macs.
Browser for most cases, Automator if you're doing it often. Convert your PDF to JPG in a browser.